Started working on a REPL helper

repl/evaldisplay.go

@@ -0,0 +1,37 @@
+package repl
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"ucl.lmika.dev/ucl"
+)
+
+func (r *REPL) EvalAndDisplay(ctx context.Context, expr string) error {
+	res, err := r.inst.Eval(ctx, expr)
+	if err != nil {
+		return err
+	}
+
+	return displayResult(ctx, r.inst, res)
+}
+
+func displayResult(ctx context.Context, inst *ucl.Inst, res any) (err error) {
+	switch v := res.(type) {
+	case nil:
+		if _, err = fmt.Fprintln(os.Stdout, "(nil)"); err != nil {
+			return err
+		}
+	case listable:
+		for i := 0; i < v.Len(); i++ {
+			if err = displayResult(ctx, inst, v.Index(i)); err != nil {
+				return err
+			}
+		}
+	default:
+		if _, err = fmt.Fprintln(os.Stdout, v.String()); err != nil {
+			return err
+		}
+	}
+	return nil
+}